Centrifuge construction



1960 J. R. NAHRGANG El' L CENTRIFUGE CONSTRUCTION Filed Oct. 17, 1955 0 PP m Q Q m NS Q u n E M. Q Q NM. NM \N @h 1 Q ZN O u l ll miUHH & mm

m 0 mm s M Q QM mm mm h \@m an a INVENTORS JAMES B. NAHRG'A/VG HAROLD H, POMEROY 14 770/? N E Y:

United States Patent CENTRIFUGE CONSTRUCTION James R. Nahrgang, Teaneck, NJ., and Harold H. Pomeroy, Burlingame, Calif., assignors, by mesne assignments, to Dorr-Oliver Incorporated, Stamford, Conn., a corporation of Delaware Application October 17, 1955, Serial No. 540,924

6 Claims. (Cl. 233-29) This invention relates generally to centrifuge machines adapted to be continuously supplied with a feed material for separating and/ or thickening operations.

One type of continuous centrifuge that has been widely used in various industrial processing operations employs a so-called return circuit whereby a large amount of the underflow material discharged from the underflow nozzles is continuously returned back into the centrifuge chamber for retreatment. Such machines are disclosed for example in Patents 1,923,454, 2,559,453, 2,616,620 and 2,625,321. The return principle makes it possible to operate such machines on feed materials containing solid particles, such as various slurries. In certain instances the feed material may contain dissolved or colloidal solids which tend to promote foaming, in which event the separating efliciency may be seriously impaired unless the machine is operated at a greatly reduced capacity.

In general it is an object of the present invention to provide an improved centrifuge capable of operating with good capacity and separating efl'iciency upon fluid feed materials tending to foam.

Another object of the invention is to provide an improvement to machines of the general type disclosed in said patents, particularly with respect to the means employed for supplying the feed into the separating chamber of the machine.

Additional objects and features of the invention will appear from the following description in which the preferred embodimenthas been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a side elevational view in section illustrating a centrifuge incorporating the present invention.

Figure 2 is a cross-sectional view taken along the line 2-2 of Figure l.

The machine illustrated in the drawing is somewhat similar to that disclosed in Patent 2,625,321. In general it consists of a rotor 11 disposed within the housing 12. Underflow discharge nozzles 13 on the periphery of the rotor deliver material into the volute 14, from which it is removed by way of external piping (not shown). A large part of such underflow material is returned back into the rotor by way of the upwardly directed nozzle 15, at the lower end of the housing. The lower end portion 11a of the rotor forms an impeller, which delivers material, through the radially extending passages 16, to the main centrifuge chamber 17. The outer regions communicating with nozzles 13 are shown separated by the generally triangular shaped hopper blocks 17a.

At the top of the housing there is a chamber 18 adapted to receive feed material, and which communicates with a downwardly extending passage 19 formed between the concentric sleeves 21 and 22. These sleeves are concentric with the vertical shaft 23 of the rotor, which extends upwardly to suitable bearing and driving means.

The rotor consists in part of an inner conical shaped member 24, which has a hub 26 for attachment to the lower end of the shaft 23. Fitted within the rotor and 'Patented Feb. 2, 1960 seated upon the member 24, there is an annular member 27 that is upwardly convergent, and which forms a feed well. The lower end of the member 27 is provided with the conical shaped skirt 29, above which are disposed the spaced separating disks 30. Member' 27 is provided with the circumferentially spaced external vertical vanes 31, and with the circumferentially spaced internal vanes 32, which impart rotary motion to feed material. A hub 33 is carried by the inner edges of the vanes, and is seated upon the hub 26. i

The centrifugally separated overflow progresses upwardly through spaces between the vanes 31, and isdischarged from the overflow lip 34, into the overflow volute 36. Suitable pipe connections are made with the volute 36 for removal of the overflow material. a

Without additional parts other than as described above, the feed material delivered downwardly through passage 19 and into the feed well is acted upon by the vanes 32 and caused to be delivered through the passages 38 to the main centrifuge chamber 17. As previously pointed out, when the liquid feed is of such a material that it is subject to foaming, the capacity of the machine may be seriously restricted if desired separating requirements are to be ma ntained.

In accordance with the present invention, we provide means within the feed well which acts upon the feed material in such a manner as to deliver it into the body of feed material maintained centrifugally upon the inner' surface of member 27, and such delivery is effected in such a manner as to avoid the detrimental effects otherwise experienced. Thus, as illustrated in the drawing, we provide a barrier in the form of a flat metal disk 39 which preferably is mounted upon the hub 33 and disposed below the lower end of the passage 19. It will be noted that thevanes 32 are cut away to accommodate the disk 39, thus provid ng vane portions 32a which extend upwardly from the horizontal plane of the disk, and portions 3215 which directly underlie thedisk. The inner edges 40 of the vane portions 32a are substantially coincident with a cylindrical surface which coinc des with the periphery of the disk 39. The disk can be mounted on the hub 33 by suitable means such as screws, pins or the like, and a seal is formed between the disk and the hub 33, and between the disk and the shaft, by suitable sealing means such as a gasket 41.

Operation of the machine as described above is as follows: Fluid feed material introduced continuously through the passage 19 is discharged with a more or less broken or indiscriminate surface into the upper part of the feed well and upon the disk 39. Rotation of this disk causes the feed material to berotated and delivered outwardly over the d sk, and to form a compact fluid layer which moves outwardly under centrifugal force. At the outer margin of the disk. 39, the material is received without splashing in a compact layer of feed material held centrifugally on the inner surface of member 27, and which in depth (by proper control of the rate of feed) is suificient to submerge the inner edges 40 of the vane portions 32a. Under such cond tions the outer margin of the disk 39 is likewise submerged in the layer of feed material maintained on the inner surface of member 27. The layer of feed material maintained along the inner surface of member 27, flows downwardly through the annular space surrounding the outer periphery of disk 39 and into the lower part of the well space below the dsk. From thence the material flows smoothly through the radially extending passages 38, into the main centrifuge chamber.

Assuming that the feed material is one containing a proteinaceous or other compound tending to cause serious foaming, the disk 39 causes some defoaming and deaeration by'virtue of the fact that material delivered upon this'disk' is caused to merge into'aeompact'film or layer of material being delivered outwardly into the compact layer of material upon the inner surface of member 27. Such movementof'material from the disk to, the walls of. the feed Welland from thence downwardlyand outwardly into the centrifuge chambers, occurs without re- -entrainment of air and in general under such conditions as to inhibit foaming.

'In actual practice it has been foundfthat the constructionidescribed above makes possible greatly increased capacity'for various feed materials subject to serious 'foaming. Thus where feed materials have afforded difficulty with conventional equipment, with the present inventionit has been possible to maintain a relatively high feed rate with good separating efficiency.

We claim: 1. In a centrifuge constructiomarotorformed to provide a separating chamber, a vertical rotatable shaft on "which'the'rotor is mounted, an annular member within "therotor and surrounding the shaft, said member forming a feed well space surrounding the shaft, means forming outwardly extending passages for delivering feed material from the lower. part of the well space into the separating chamber of the rotor, a flow control disk fixed to rotate "with the shaft within said feed well and separating the upper and'lower portions of the same, said disc being dimensioned whereby an annular passage extends about "theperiphery of said disk for flow of feed material therethrough between the upper and lower portions of the feed well, vanes mounted within the upper and lower portions of'the feed well and serving to impart rotary motion to feed material, and means for delivering feed material downwardly and upon said disk, whereby such mater'al.

vide a separating chamber, a vertical shaft extending centrally of the rotor, a hub carried by the rotor and V serving to mount the rotor upon "the"lower' encl of the shaft, an annular member within the rotor and surrounding the shaft and serving to form a feed well space, said space extending above and below the upper end of the hub, means forming outwardly extending passages for delivering feed material from the lower part of the well space into theseparating chambenia'iflowcontrol disk mounted upon the upper end of the hub, means for delivering feed material downwardly -into the-upper-part of the feed well and upon the upperface. of the control disk, the dimensioning of the control diskbeing such as to provide an annular flow passabe between said member and the outer. periphery of .thepdiskythrough'which feed material may flow from the upper to the lower parts of the feed well, and vane means withinsaid feed well and said passages serving to impart rotary motion to feed material, said vane means including vane portions extending above the level of the control diskin the upper part of the feed well, said portionshavingtheir inner edges substantially coincident with a cylinder-which is also coincident with the outer periphery of the control disk.

5. A centrifuge construction as in claim 4 in'which the control disk is sealed with respect to the spaces on opposite sides of'the same, exceptfor said annularpas sage.

6. In a'centrifuge construction, a rotorformed'to provide a separating chamber, a vertical rotatableshaft on which the rotor is mounted, an annular member within the rotor forming a feed well,-means forming passages extending outwardly from the lower part of the feed well for delivering feed material into the separating chamber, an annular flow control barrier disposed within said feed well abovesaid passages and fixed to rotate with i the shaft, and means for introducing feed material into the portion of the feed well above said barrier, said barrier being dimensioned to provide an annular space about the periphery for flow of feed material 'through the same.

References Citedin the file" of this patent UNITED STATES PATENTS 1,954,676 Lindberg Apr. 10, 1934 2,294,468 Lindgrew Sept. 1, 1942 2,478,992 Wheelwright Aug. 16, 1949 

